Landsat Turns 45!

False colour image of Dallas, Texas. The first fully operational Landsat image taken on July 25, 1972, Image courtesy: NASA’s Earth Observatory

Landsat has celebrated forty-five years of Earth observation this week. The first Landsat mission was Earth Resources Technology Satellite 1 (ERTS-1), which was launched into a sun-synchronous near polar orbit on the 23 July 1972. It wasn’t renamed Landsat-1 until 1975. It had an anticipated life of 1 year and carried two instruments: the Multi Spectral Scanner (MSS) and the Return-Beam Vidicon (RBV).

The Landsat missions have data continuity at their heart, which has given a forty-five year archive of Earth observation imagery. However, as technological capabilities have developed the instruments on consecutive missions have improved. To demonstrate and celebrate this, NASA has produced a great video showing the changing coastal wetlands in Atchafalaya Bay, Louisiana, through the eyes of the different Landsat missions.

In total there have been eight further Landsat missions, but Landsat 6 failed to reach its designated orbit and never collected any data. The missions have been:

  • Landsat 1 launched on 23 July 1972.
  • Landsat 2 launched on 22 January 1975.
  • Landsat 3 was launched on 5 March 1978.
  • Landsat 4 launched on 16 July 1982.
  • Landsat 5 launched on 1 March 1984.
  • Landsat 7 launched on 15 April 1999, and is still active.
  • Landsat 8 launched on 11 February 2013, and is still active.

Landsat 9 is planned to be launched at the end 2020 and Landsat 10 is already being discussed.

Some of the key successes of the Landsat mission include:

  • Over 7 million scenes of the Earth’s surface.
  • Over 22 million scenes had been downloaded through the USGS-EROS website since 2008, when the data was made free-to-access, with the rate continuing to increase (Campbell 2015).
  • Economic value of just one year of Landsat data far exceeds the multi-year total cost of building, launching, and managing Landsat satellites and sensors.
  • Landsat 5 officially set a new Guinness World Records title for the ‘Longest-operating Earth observation satellite’ with its 28 years and 10 months of operation when it was decommissioned in December 2012.
  • ESA provides Landsat data downlinked via their own data receiving stations; the ESA dataset includes data collected over the open ocean, whereas USGS does not, and the data is processed using ESA’s own processor.

The journey hasn’t always been smooth. Although established by NASA, Landsat was transferred to the private sector under the management of NOAA in the early 1980’s, before returning to US Government control in 1992. There have also been technical issues, the failure of Landsat 6 described above; and Landsat 7 suffering a Scan Line Corrector failure on the 31st May 2003 which means that instead of mapping in straight lines, a zigzag ground track is followed. This causes parts of the edge of the image not to be mapped, giving a black stripe effect within these images; although the centre of the images is unaffected the data overall can still be used.

Landsat was certainly a game changer in the remote sensing and Earth observation industries, both in terms of the data continuity approach and the decision to make the data free to access. It has provided an unrivalled archive of the changing planet which has been invaluable to scientists, researchers, book-writers and businesses like Pixalytics.

We salute Landsat and wish it many more years!

The Satellite Earth Observation Industry Began …

The satellite Earth observation (EO) industry, arguably, began 37 years ago yesterday. Now, before everyone starts tweeting and emailing hear me out. Although by this date EO satellites were in orbit, data successfully collected and imagery produced, the concept of a sustainable industry really began on the 6th January 1978 with the deactivation of Landsat-1.

Landsat 1 Image of East Anglia June 1976

Image of East Anglia, UK taken by Landsat 1 in June 1976; data courtesy of the European Space Agency / U.S. Geological Survey.

Landsat-1, also known as ERTS-1 (Earth Resources Technology Satellite), was launched by NASA into a sun-synchronous near polar orbit on the 23rd July 1972. It carried two sensors:

  • Return Beam Vidicon (RBV) which only operated for 14 days and recorded only 1692 images; and
  • Multispectral Scanner operating in four bands with a non-square sampling interval (pixel size) of 57m x 79m, that’s now resampled to 60m resolution imagery.

Landsat-2 was launched on 22nd January 1975 and carried exactly the same sensors as its predecessor; and it is this continuity of data that gave birth to the Earth observation industry. It paved the way for the development of an archive of over forty years worth of additional data provided by Landsat-3, Landsat-4 and Landsat-5; unfortunately, Landsat-6 did not reach its orbit. The archive continues to grow through the currently active Landsat-7 and Landsat-8, but it all began with Landsat-1.

The concept of a global archive gives satellite remote sensing its unique selling point. No other method of measurement or imagery has the ability to provide global coverage, almost real time data, time-series data analysis and the opportunity to go back and retrieve data before you knew you needed it! These elements, together with scientific knowledge and computing power, are the backbone of the products and services that form the modern EO industry.

The second Landsat driver to enhance the EO industry occurred thirty years after the deactivation of Landsat-1, when a data policy change in 2008 meant that all new and archived Landsat data held by the United States Geological Survey (USGS) was made freely available, via the internet, to anyone in the world.

In addition, in researching this post I also discovered that Landsat-1 has an island named after it. A Canadian coastal survey was carried out in 1976 using Landsat-1 data, and a number of unchartered features were discovered off the northeast coast of Labrador. Landsat Island is 20km off the coast and has a landmass of only 25m x 45m, with the only known inhabitant a polar bear! The island marks the easternmost point of the Canadian land mass; and its discovery increased Canada’s territorial waters by 68km.

Landsat first day cover

Landsat first day cover

Since the first Landsat was launched, many more EO satellites have gone into orbit; our blog post last year noted 192 EO satellites in orbit at the start of 2014. However, it’s worth remembering that although Landsat was not the first EO satellite, the Landsat missions are the founding fathers of the EO industry through their foresight of data continuity.